Characterization of fluctuations in the JET Divertor plasmas with Langmuir probes

Abstract

Langmuir probe tips embedded in the divertor and X-point sweeping provide JET with high spatial resolution profiles of fluctuations. Broadband fluctuation spectra have been observed in the divertor plasma strike zones with the absolute and relative level of fluctuations increasing when crossing the separatrix from the scrape-off layer into the private flux region. Asymmetries in the fluctuation levels measured at the inner and outer divertor plates have been observed with a higher level of fluctuations at the outer target. Fluctuation levels are altered by the L - H transition, with the strongest modification in the proximity of the separatrix. A significant rise in the relative level of fluctuations has also been observed in detached plasmas in comparison with attached plasmas.